The present invention relates generally to the field of pulmonology, and more particularly to the field of chronic obstructive pulmonary disease. In this regard, the invention provides devices and methods that are useful in improving breathing in patients with chronic pulmonary disease.
Chronic obstructive pulmonary diseases (COPD) is both very common and increasing in incidence. COPD is the fourth most common cause of death in this country and the morbidity and mortality it causes continue to increase.
COPD comprises chronic bronchitis and emphysema. In both chronic bronchitis and emphysema, airflow obstruction limits the patient's air flow during exhalation. COPD is a progressive disease characterized by worsening baseline breathing status over a period of many years with sporadic exacerbations often requiring hospitalization.
Typically, patients with COPD have extensive smoking histories; smoking is the major risk factor for development of COPD. Symptoms typically begin in the fifth decade of life with progression to dyspnea on exertion during the sixth and seventh decade. Early symptoms include increasing sputum production, and sporadic acute exacerbations characterized by increased cough, purulent sputum, wheezing, dyspnea, and fever. As the disease progresses, the acute exacerbations become more frequent. Late in the course of the disease, the patient may develop hypercapnea, hypoxemia, erythrocytosis, cor pulmonale with right heart failure, and edema.
Though both chronic bronchitis and emphysema lead to chronic obstruction leading to limitation in expiratory flow, the pathophysiology and clinical presentation of each disease are different. Chronic bronchitis is characterized by chronic cough with sputum production leading to obstructed expiration. Pathologically, there is mucosal and submucosal edema and inflammation and an increase in the number and size of mucus glands. Emphysema is characterized by destruction of the lung parenchyma leading to loss of elastic recoil, reduced tethering of airways, and obstruction to expiration. Pathologically, the distal airspaces are enlarged.
Management of COPD is largely medical and infrequently surgical. Initially, exercise and smoking cessation are encouraged. Medications including bronchodilators (including beta-agonists, anti-cholinergics, and theophylline) and anti-inflammatories are routinely prescribed but are by no means curative. Pulmonary rehabilitation is often prescribed and has been shown to improve quality of life and sense of well being. Long term oxygen is generally reserved for the more severely affected patients. Surgical options are limited and include lung volume reduction surgery and lung transplantation. Both of these surgical options, because of associated morbidity, are infrequently performed.
One of the important components of the aforementioned pulmonary rehabilitation is breathing retraining. This involves teaching the patient new breathing techniques that reduce hyperinflation of the lungs and relieve expiratory airflow obstruction. One of the goals is of course to reduce the level of dyspnea. Typically, these new breathing techniques include diaphragmatic and pursed-lip breathing. This latter technique, pursed-lip breathing, involves inhaling slowly through the nose and exhaling through pursed-lips (as if one were whistling), taking twice as long to exhale as to inhale. Most COPD patients instinctively learn how to perform pursed-lip breathing in order to relieve their dyspnea.
The belief among the medical community is that by producing a proximal obstruction (pursing the lips), the effect is to splint open the distal airways that have lost their tethering. In other words, the affected airways that would normally collapse upon themselves remain open when the patient breathes through pursed-lips.
Medical literature has confirmed the utility of pursed-lip breathing in COPD patients. Specifically, it has been found that respiratory rate is reduced, tidal volumes are increased, and oxygen saturation is improved. All of these contribute to improved dyspnea on the part of the patient. The drawbacks of pursed-lip breathing are twofold. First, because it requires conscious effort, the patient cannot breath through pursed lips while sleeping. As a result, the patient can still become hypoxic at night and may develop pulmonary hypertension and other sequelae as a result. Second, since the patient has to constantly regulate his own breathing, this interferes with his performing other activities.
Clearly, there is a need for a medical device and/or procedure that mimics the effect of pursed-lip breathing without suffering from the above drawbacks. As such, there is much interest in the development of new medical devices and methods for use in procedures for patients with COPD.